Drive trains of vehicles, especially of all-terrain vehicles, which possess at least one driving machine, one multi-group transmission and one output drive, have been known in the practice for a considerable time. The formation of a drive train with a multi-group transmission is undertaken when a multiplicity of gear stages with the fewest possible gear pairs is to be made available.
Multi-group transmissions, in general, incorporate a combination of a plurality of individual transmissions grouped in a series arrangement. The transmission groups can be designated as the so-called forward shifting groups (in order of power flow), a main transmission and a so-called after-shifting groups, which are known as range groups. If a main transmission of a multi-group transmission is constructed as an automatic transmission, then a greater degree of driving comfort is made available to a driver, in that a multitude of gear stages become available. Such an automatic transmission can be comprised of six gear stages for forward travel and one gear stage for reverse movement.
Range groups are characterized, when present as transmission groups of multi-group transmissions, in that an input speed of rotation to the range group is always in the “slow” stage, where a substantial increase in torque takes place simultaneously. Because of the high torque increase, range groups in a multi-group transmission are always placed to follow in a following position in regards to the main transmission, in order to avoid running the exceedingly high torque through the main transmission.
Constructively applicable formations of range groups in practice, include the use of either counter forward transmission groups or planetary gear transmissions, wherein the latter design offers a more compact alternative and has the advantage of lesser installation space.
A change of a ratio in a range group is executed by a shifting element, whereby shifting can be made between a first ratio “low” and a second ratio “high”. With this arrangement, and when in a first selected low gear of the range group and in combination with the main transmission, the driver has a choice of ratios available, which are an advantage for operation of a vehicle in a terrain characterized by steep climbs and wherein slow vehicle speeds are acceptable.
The second ratio “high” is less subject to losses, so that when traveling under normal condition of terrain and also at higher driving speeds, shifting into the second ratio “high” is to be preferred.
Experience in actual practice has indicated that where conventional procedures for control of a drive train are concerned, a disadvantage is present, i.e., a gear stage of a multi-group transmission demanded by an activated shifting program, is formed through a combination of a ratio of the main transmission and the ratio “low” of the range group, even though the demanded ratio of the multi-group transmission could also be achieved by a combination of the ratio “high” of the range group and a corresponding ratio of the main transmission; this being in order to avoid the transfer of a higher torque through the main transmission.
The purpose of the present invention is to provide a method for the control of a drive train of a vehicle available by which a multi-group transmission can be driven at a high degree of efficiency.